Advancements in communication technologies have permitted the introduction of, and popularization of, new types of communication systems. As a result of such advancements, the rate of data transmission and the corresponding amount of data, permitted to be communicated in such communication systems, has increased.
A radio communication system is representative of a type of communication system which has benefited from advancements in communication technologies. A radio communication system inherently permits an increase in communication mobility as communication channels defined in such a system are formed of radio channels and do not require wireline connections for their formation. A radio communication system, however, typically is bandwidth-limited. That is to say, a frequency bandwidth permitted to be utilized in a radio communication system is regulated by regulatory bodies. Generally, only a limited amount of the electromagnetic spectrum is allocated for usage by a particular radio communication system. Because the spectrum allocation for use by a particular system is limited, communication capacity increase of a radio communication system is sometimes limited by such allocation. Increase of the communication capacity of the radio communication system, therefore, is sometimes only possible if the efficiency by which the allocated spectrum is used is increased.
Digital communication techniques, for instance, provide a manner by which to increase the bandwidth efficiency of communications in a communication system. The use of digital communication techniques is particularly advantageously implemented in a radio communication system due to the particular needs to efficiently utilize the spectrum allocated to such a system.
When digital communication techniques are used, information which is to be communicated is typically digitized. In one technique, the digitized information is formatted into packets, and the packets are communicated to effectuate the communication. Individual ones, or groups, of the packets of data can be communicated at discrete intervals and, once communicated, concatenated together to recreate the informational content contained therein.
Because packets of data can be communicated at discrete intervals, a communication channel need not be dedicated solely for the communication of packet data generated by one sending station to one receiving station as conventionally required in circuit-switched communications. Instead, a single channel can be shared amongst a plurality of different sending and receiving station-pairs. Because a single channel can be utilized to effectuate communications by the plurality of pairs of communication stations, improved communication capacity is possible.
In some digital communication systems, a random access channel is defined upon which to permit the communication of the packet of data. A sending station which is to send a packet of data is permitted random access to the random access channel. While such a scheme advantageously provides a simple manner by which to effectuate communication of packets of data, lack of coordination between separate sending stations might result in two sending stations attempting to transmit a packet of data at the same time. In such an occurrence, referred to as a collision, the packets of data transmitted at the overlapping times by the separate communication stations, interfere with one another to prevent successful communication of either packet of data.
A slotted-ALOHA technique is an existing, random access protocol by which to communicate packet data on a random access channel. In such protocol, when a packet of data is successfully communicated to a receiving station, the receiving station returns a feedback acknowledgment to the sending station to inform the sending station of the successful communication of the packet of data. If, also, a determination is made at the receiving station of inadequate communication of the packet data due to a collision condition or other errors resulting from transmission of the packet on the random access channel, the feedback acknowledgment returned to the sending station indicates an unsuccessful transmission. Responsive to a feedback acknowledgment of an unsuccessful transmission, the packet is caused to be retransmitted by the sending station.
Back-off schemes, such as a binary exponential back-off scheme, have been implemented to minimize the occurrence of collisions by exploiting the feedback acknowledgments returned by a receiving station. Back-off schemes generally provide an improved manner of effectuating retransmission of packets of data from such sending stations. A sending station, also referred to herein as a terminal, is referred to as being backlogged if a prior transmission of the packet of data is not successfully received at a receiving station.
Packet data communications are effectuated, for instance, in conventional LANs (local area networks). Wireless networks, operable in manners analogous to, wired LANs have also been developed and are utilized to communicate packets of data over a radio link upon which a random access channel is defined.
For example, a broadband radio access network (BRAN) standard promulgated by the ETSI sets forth a standard for operation of a wireless LAN operable in the 5 GHz range. In this standard, a medium access control (MAC) frame structure is defined. The MAC frame structure includes a BCH (broadcast channel), a DLCH (down-link channel), an ULCH (up-link channel), and a RACH (random access channel). An IBCH (inband control channel) is sometimes defined upon the BCH or upon the DLCH. The IBCH is a logical channel. In the system defined by BRAN, as well as other wireless LANs, mobile terminals are utilized by users of the network to effectuate telephonic communications. The telephonic communications include, for example, voice as well as data, communications.
In the system defined by the BRAN standard, a mobile terminal transmits packets of data to an access point (AP) on the random access channel. The access point forms a portion of the infrastructure of the LAN. If a determination is made that the packet is successfully communicated to the infrastructure, the access point responds with a feedback acknowledgment indicating the successful delivery of the packet. If, conversely, a collision condition or other error resulting in unsuccessful transmission occurs, the access points return a feedback acknowledgment indicating the occurrence of the unsuccessful transmission.
Determination at the infrastructure of whether the transmission of the packet of data is successful requires processing at the infrastructure, such as to decode the received packet. Such processing requires a time period, i.e., processing time, which corresponds to a time period which may exceed that of the time period within which a MAC frame is formed. The feedback acknowledgment is returned to the mobile terminal, e.g., on the broadcast channel an IBCH (inband control channel) or first portion of the MAC, or other, frame. And, because of the processing time, together with the requirement that the feedback acknowledgment be formatted to be transmitted in the broadcast, or other appropriate, channel, the mobile terminal does not receive an immediate acknowledgment as to whether or not the prior transmission of the packet has been successfully completed. That is to say, the feedback acknowledgment is returned to the mobile terminal in a frame subsequent to the frame in which the packet is transmitted. In a conventional protocol, the mobile terminal retransmits the packet of data subsequent to detection of a feedback acknowledgment indicating unsuccessful transmission of the packet.
The existing requirements limit the data throughput rates as the feedback is required to be detected at the mobile terminal prior to retransmitting a packet of data. If a manner could be provided by which to more quickly select when to retransmit a packet of data, the data throughput rate of the communication system could be improved.
It is in light of this background information related to the communication of packet data that the significant improvements of the present invention have evolved.